Fast track formulation pH screening with automated buffer exchange on Big Tuna

Importance of Topic

Optimizing buffer conditions and pH is critical in biologics development because protein stability—conformational, chemical and colloidal—depends heavily on formulation parameters. Traditional manual buffer exchange is laborious and inconsistent, limiting throughput in formulation screening.

Objectives and Study Overview

This study demonstrates how the Big Tuna automated ultrafiltration/diafiltration system enables high‐throughput pH screening of a monoclonal antibody (mAb). A mAb formulated in 20 mM histidine was exchanged across a pH range of 6.3–7.4 in duplicate, using a Unfilter 24 plate (4 mL per well) to generate 12 test formulations in a single run.

Methodology and Instrumentation

Big Tuna employs pressure‐based filtration with gentle orbital mixing to automate buffer exchange. Key parameters included:

• Target exchange per pool: 96 %
• Volume removal per cycle: 33 %
• Initial and final well volume: 4 mL
• Initial and final mAb concentration: 45 mg/mL

Instrumentation:

• Big Tuna automated UF/DF system
• Unfilter 24 regenerated cellulose plate (10 kDa cutoff, 0.45–8 mL per well)
• Ultrasonic volume sensor for real‐time volume monitoring
• Stunner spectrophotometer for concentration measurement
• Big Tuna Client software for protocol design and data export

During the run, Big Tuna alternated filtration, volume measurement, and buffer refill, adjusting pressurization cycle duration to maintain uniform exchange across all wells.

Key Results and Discussion

The system completed ten exchange cycles in approximately 7.1 hours total, with an average cycle duration of 21 minutes (range 19–22 min). Final well volumes averaged 4,004 ± 15 µL, and final mAb concentrations were 45.3 ± 0.3 mg/mL, matching the initial target. Percent exchange per pool averaged 97.9 % (min 96.5 %, max 99.1 %), confirming consistent buffer replacement across all 12 formulations.

Benefits and Practical Applications

Automating pH screening with Big Tuna offers:

• Increased throughput: up to 24 or 96 samples per run
• Reproducible sample handling and precise volume control
• Minimal hands‐on time, freeing resources for other tasks
• Real‐time adjustment of filtration cycles for uniform exchange

These features accelerate formulation development and enable more systematic screening of stability conditions.

Future Trends and Potential Applications

Advances may include:

• Integration with high‐throughput analytical techniques (e.g., MS, DLS)
• Automated screening of additional variables such as ionic strength, excipients and surfactants
• AI‐driven experimental design for formulation optimization
• Scale‐up to pilot and manufacturing workflows for process consistency

Conclusion

The Big Tuna automated UF/DF platform successfully conducted a high‐throughput pH screen on a mAb, delivering consistent buffer exchange, high protein recovery and reduced manual effort. This approach streamlines early‐stage formulation development and supports robust decision‐making in biologics pipelines.